The invention relates to a torque-transmitting device, particularly for motor vehicles, with a prime mover unit such as a combustion engine with a driving shaft, a speed-changing transmission with a transmission input shaft, and a hydraulic coupling device between the prime mover unit and the transmission, i.e., a fluid coupling such as a Fottinger coupling, or a hydrodynamic torque converter, consisting of at least a pump wheel connected to the torque-input side and a turbine wheel connected to the torque-output side, as well as in some cases a stator wheel interposed between the pump wheel and the turbine wheel, and at least one housing solidly connected to the pump wheel and containing the turbine wheel.
Devices of this kind have been known for a long time and have been optimized for a great variety of diverse tasks and requirements. In order to completely disengage the torque-transmitting unit from the prime mover unit, DE-OS 40 07 424 proposes the use of a mechanical clutch arranged outside of the housing between the prime mover unit and the torque-transmitting unit, where the mechanical clutch either comprises a separate piston housing for the hydraulic control of the clutch or requires the axial displacement of a housing shell for disengaging the clutch. Thus, the proposed solution requires more space in the axial direction and is expensive to implement.